Blister packaging is known for receiving a product, e.g., in tablet, powder, or other form, wherein each of the individual recesses or compartments of the base substrate can be provided with a product and the packaging can then be sealed with a cover layer, e.g., in the form of a lidding film. The lidding film must seal to the base substrate on sealing surfaces provided between the recesses, whereby the lidding film encloses the product filled recesses of the base substrate. As a result, the packaged product is sealed tight against the exterior environment and each individual product in the various compartments is separated from one another.
The method and degree of difficulty encountered in opening such blister packaging is often tailored to the intended user, wherein packaging for seniors may be made relatively user friendly (easier to open) while other packaging may be designed to be more difficult to open (e.g., child resistant). Still other packaging is designed for tamper resistance. In some packaging the cover layer can be removed by peeling, while in others the cover layer is broken by pushing the product through the cover layer to remove the product from the compartment. It will be understood that the base substrate and cover layer may include multiple layers and multiple materials that serve different functions.
In addition to designing for an intended use (e.g., ease of opening, size and composition of product, designated shelf-life), the packaging designer must account for the number and complexity of the steps and the expense of the equipment required to form the single or multilayer components, to assemble them into a package, and to fill the individual compartments with the product. Also relevant is the recyclability of the various components.
One type of blister packaging, referred to as “bend and peel”, is formed from a polyvinyl chloride (PVC) base substrate, and attached cover layer, wherein an edge portion of the package can be bent back by the user along a reduced thickness score line, breaking the brittle PVC base substrate along the score line to form a tab from the broken off portion of base substrate and attached cover layer, thus enabling the user to grab the tab and peel off the cover from an area adjacent a product compartment in the base substrate to release the product from the package.
There are a number of problems with this bend and peel product. First it only works reliably with a brittle material like PVC; more specifically, the score depth can vary widely (e.g., in a broad range of 50-80%), and because PVC is so brittle, it will break reliably in use. However, many companies prefer not to use PVC for packaging, because the consumer recycling stream is not as well established as it is for other materials. Attempts to use other materials that are substantially less brittle than PVC, such as polyesters, have failed because they require a much tighter range of score depth to ensure that every user can bend and reliably break the package along the score line. For example, using a polyester based film, such as polyethylene terephthalate (PET) film at 12 mil thickness, would require a score depth of at least 10 mils. This requires a very sharp knife to guarantee the necessary score depth. Deeper cuts such as these are difficult to accomplish without inadvertently cutting through the entire thickness. Another problem is that every film varies in thickness, so for example a 10 mil film may vary between 9.5 to 10.5 mils or even wider depending on the film production quality. This makes it impossible to guarantee the required thickness depth in any practical manufacturing operation. It further requires a very sharp knife edge for every cut, which is prohibitively expensive as the manufacturer must continually replace or re-sharpen the blade.
Thus, there is an ongoing need for materials and processes for making blister packaging that overcome the various material, process and cost limitations of the prior art.